Italy
The twin-engined fighter also attracted the attention of the authorities and manufacturers of Fascist Italy. They were in a poor position to take up the concept, because in the late 1930s the Italian aviation industry and air force were conservative, with entrenched defenders of the agile but slow biplane fighter — they fielded the last of its kind, the Fiat C.R.42. Equally harmful was a lack of modern and powerful engines. Old-fashioned structures and low engine power were probably more detrimental for heavy fighters than for any other kind of aircraft. Besides, the available production capacity was small and poorly managed, and it was impossible to build a sufficient number of these aircraft to make their development worth while.
Much of this shows in the Fiat CR.25, flown in 1937 as a twin-engined long-range fighter. Roughly the size of a Mosquito and somewhat lighter, the CR.25 had a crew of three and was powered by two Fiat A 74 RC 38 radial engines of 840 hp. With these engines and a clean but conventional design, the CR.25 had a maximum speed of 460 km/h at 5,500 m, creditable but far from brilliant. The production CR.25bis version had a modest armament of just two fixed 12.7-mm Breda-SAFAT machine guns and one flexible gun of the same type in a dorsal turret. Just 10 served operationally, and in defiance of their apparent vulnerability they soldiered on until 1943 without operational losses, despite clashes with Hurricanes, Blenheims, Beaufighters and even P-38s.
A compact aircraft produced by IMAM took the other path in the development of twin-engined fighter. The Ro 57 was a bit smaller even than the Whirlwind, and powered by the same A 74 RC 38 radials as the CR.25. The Ro 57 was considerably slower than the Whirlwind, however, with a top speed of 500 km/h, and carried much weaker armament, just two 12.7-mm machine guns. A less advanced structural and aerodynamic design appears to have been the cause, although the Italian fighter took to the air a bit later, making its first flight in early 1939. Official doubts about the usefulness of this type of aircraft and its ability to survive combat with single-engined opponent took its toll, and the Ro 57 finally entered limited service as a fighter-bomber in early 1943. It is useful to compare this with the development time of the Whirlwind, which was judged by the RAF to have been far too long: That of the Ro 57 took about two years more!
The Caproni firm, founded by Gianni Caproni, had made its reputation during the First World War as the manufacturer of large bombers. The typical Caproni aircraft of the immediate post-WWI period were sesquiplanes, but in the early 1920s drawings were made for a twin-engined monoplane fighter of all-metal construction, with a blunt-nosed fuselage, a cantilever wing, corrugated metal skinning and fixed landing gear. A quite radical design for the time, this Ca.65 was not built.
The firm had another opportunity in 1940 when Caproni built the elegantly streamlined Ca.331. This aircraft possesed a modern all-metal monocoque structure, highly streamlined lines, two 750 hp air-cooled in-line Delta RC.35 engines, and in its initial reconaissance version, a smooth transparent nose. In May 1942 the air force ordered the conversion of the second prototype in a nightfighter version, with a stepped cockpit and a solid nose, four 20-mm MG 151/20 cannon, two 12.7-mm Breda-SAFAT machine guns, and a flexible Breda-SAFAT in a dorsal and ventral defensive position. While the aircraft looked good, it was underpowered for a fighter, even after the installation of 800 hp engines or with the planned 850 hp engines. Top speed of the production version would have been 505 km/h at 5300 m, but Italy surrendered before production could be seriously contemplated.
SIAI-Marchetti contributed one of the more radical concepts. The S.M.91 had the same general configuration as the Lockheed P-38 Lightning, twin tails booms connected by a tailplane and a central nacelle for the crew. The S.M.91 was rather bigger and heavier than the P-38, however, with a crew of two and about a third more wing area. As flown in March 1943 with 1,290 hp Daimler-Benz DB 605A-1 engines, the top speed was a modest 585 km/h at 7,000 m. In the hope of reducing drag and increasing performance, the team developed the S.M.92 in parallel; this had no central nacelle, and the crew was accommodated in a cockpit in the left-hand tail boom. Armament had to be relocated as well, and while the the S.M.91 had three MG 151/20 cannon in the nacelle and two more close to it in the wing roots, the S.M.92 had two cannon in the centre wing section, one cannon installed to fire through the hub of the right-hand engine, and two synchronized machine guns on each engine. One more gun, firing aft, was installed on the tailplane. The S.M.92 was briefly flown by the Germans after the Italian surrender.
Probably the most promising of the Italian designs was the IMAM Ro 58, a clean all-metal design with twin tail fins, 1160 hp Daimler-Benz DB 601A-1 engines, and an armament of five 20-mm MG 151/20 cannon and a flexible 12.7-mm. The prototype made its first flight in May 1942 and was highly praised, but again the surrender of Italy in August 1943 prevented any production from taking place. It fate was thus the same as that of the last generation of Italian single-engined fighters, which were also compared favourably with German aircraft powered by the same engines, but were built in too small numbers to have any impact.
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